The purpose of the present invention was to produce an integral skin foam using water as the sole blowing agent, while still retaining the dense, largely noncellular surface layer characteristic of foams blown with organic blowing agents.
Water-blown integral skin polyurethane foams are known in the art. See, e.g., U.S. Pat. Nos. 5,132,329, 5,166,183, 5,216,035, 5,284,880, 5,300,532 and 5,338,820. In general, such foams are prepared by reacting isocyanates with polyols in the presence of water. With most combinations of catalysts, water-blown foams have uniform properties throughout. In other words, the physical properties measured at the surface of the molded product are very nearly the same as those measured on foam in the core of the molded product.
The use of diorganotin sulfides in combination with tertiary amine catalysts to produce polyurethane foams is described in U.S. Pat. Nos. 3,822,223 and 4, 119,585.